1. Field of the Invention
This invention pertains to the general field of water purification and recovery. In particular, it provides a new method and apparatus for the reclamation and reuse of waste-water effluent from wash cycle of laundry operations.
2. Description of the Prior Art
Normally, water usage results in its contamination and the resulting waste water is no longer useful for most applications. Therefore, waste waters from domestic and industrial users have been the subject of treatment and purification for a long time in order to remove toxic contaminants, bad odors and suspended solids. The waste water is typically treated by various means of filtration and chemical reaction designed to accomplish specific purification goals, as needed by particular users. The most common systems involve passing the water through layers of filtering media to remove solid particles and through chemically active media to reduce the water's hardness, improve its pH, and extract undesirable contaminants.
Accordingly, water purification agents are generally categorized in terms of their function as filters, when designed to eliminate larger size suspended solids; clarifiers, when intended to remove smaller size particles and reduce opacity; softeners, to remove calcium and magnesium ions and reduce water hardness; and refiners, to extract chlorine, iron and organic compounds. Both anion and cation exchange resins are used to perform a multiplicity of these functions.
The separation of solutes from water by means of selectively permeable membranes is also an effective and economical method of water purification. The processes of reverse osmosis, ultrafiltration, nanofiltration and electrodialysis all involve the use of membranes that have the ability to prevent the migration of most dissolved and suspended solids while allowing the passage of water through their pores.
This invention is directed to the use of a novel combination of these known methods of water purification in a new application for treating waste-water effluents from commercial laundries. In particular, it discloses a closed-loop system for reusing the hot waste-water effluent from the washing cycle of a laundry operation.
During conventional laundry operations, the waste water from each cycle is typically disposed of to the sewer after use and fresh water is fed to the washer machines through cold and hot feed systems to completely replace each load. The cold water feed is drawn directly from a utility supply, while the hot water feed is first heated and stored in a tank at about 150 to 180.degree. F. As the washer machines process laundry, they call for both hot and cold water from these sources in order to provide the water utilized in the wash process. In most operations, the proportion of hot to cold water usage is about fifty/fifty. The resulting waste water is typically at 120.degree. F. and laden with detergent and softening chemicals, in addition to dirt and pollutants. Therefore, when waste water is drained to a sewage system or otherwise discarded, useful chemicals and valuable heat are also wasted with it. In addition, the contaminants left in the water often require downstream water treatment before the effluent can be released to the environment.
Thus, conventional laundry operations involve large water usage, high fuel consumption for water heating, and wasteful disposal of active chemical ingredients in the waste-water effluent, all of which affect the efficiency and operating costs of a laundry.
Therefore, it would be very desirable to improve commercial laundry processes by minimizing these problems.
In U.S. Pat. No. 4,441,340 (1984), Kaplan discloses a system for recycling water from the rinse cycle of a commercial laundry. The water is combined with heated or fresh make-up water, as necessary to reach the required operating temperature, and is then used in the next wash cycle of the laundry system. By so doing, the invention also recovers the heat content present in the water after the rinse cycle is completed. Only rinse water is used because it is relatively clean and can, therefore, be reused as wash water maintaining the quality of washing during the second and subsequent cycles.
Since commercial laundries use relatively cold water for rinsing purposes, the heat recovery afforded by this invention is modest. In addition, no prior art system has been able to recycle wash water effectively and recover not only its energy content, but also its unused active chemicals. Thus, the purpose of this invention is to address this objective by reusing at least a portion of the hot waste water produced during the wash cycle of conventional laundry processes.